Atta is the flour used to make most South Asian flatbreads, such as chapati, roti, naan and puri. Most atta is milled from the semi-hard wheat varieties, also known as durum wheat, that comprise 90% of the Indian wheat crop, and is more precisely called durum atta.
Hard wheats have a high content of gluten (a protein composite that gives elasticity), so doughs made out of atta flour are strong and can be rolled out very thin.
In India and Pakistan wheat products like 'wheat powder' or 'wheat flour', 'atta flour', 'maida flour' and 'Sooji' (also known as 'rava') are available in the market.
Whole Wheat grains contain all three parts of the kernel (Kernel means a grain or seed, as of a cereal grass, enclosed in a husk). There are, mainly, three parts for a wheat grain.
(1) Germ (2%) - Embryo of the wheat kernel.
(2) Endosperm (85%) - Nutritive tissue surrounding the embryo.
(3) Bran - Multi-layered outer skin of the kernel.
Atta is the Hindi word for dough; it is used by metonymy to mean "flour used for baking".